Presentation on theme: "Gareth Berry University of Reading, UK. Evaluation of some daytime boundary layer forecast techniques. Undergraduate project presentation."— Presentation transcript:
Gareth Berry University of Reading, UK. Evaluation of some daytime boundary layer forecast techniques. Undergraduate project presentation
The Convective Boundary Layer (CBL)
Forecasting maximum day temperature from the tephigram Empirical method formulated by E.Gold (1933). Still in operational use with UK Met.Office. Makes use of pre-dawn temperature profile to forecast hourly temperature rise and daily maximum. Only works under clear skies.
Discussion points Location of data sources: - Local effects e.g. Urban heat island? - Synoptic variation? - How similar are the two sites? Subjective method.
Carson model of the CBL Uses an assumed temperature profile evolution. Assumes heat flux by entrainment is a a fixed fraction of the surface heat flux. Predicts depth of the CBL:
Carson model temperature profile
Appraisal of the Carson model Carson model with sinusoidal sensible heat flux used to predict CBL depth. Magnitude of heat flux equal to peak net radiation sensed at Reading. Carson CBL depth compared to observed CBL depth from afternoon radiosonde ascent.
Discussion points (2) Model errors: - Assumed sensible heat flux. - Length of heating. - Entrainment heating fraction. Observational errors: - Timing of radiosonde ascents. - CBL structure.
Conclusions Results using Golds Method show that the simplified temperature evolution is of practical use. Carson model results are of the same order of magnitude as the observations. Large uncertainties mainly due to lack of sufficient input data.
Future work and improvements Site all observations together. Attempt to estimate the terms in the surface energy balance. Obtain better observations of the CBL e.g. by tethered balloon.